Electron induced chemical etching for device level diagnosis

ABSTRACT

A method of imaging and identifying materials, contamination, fabrication errors, and defects on and below the surface of an integrated circuit (IC) is described. The method may be used in areas smaller than one micron in diameter, and may remove IC layers, either selectively or non-selectively, until a desired depth is obtained. An energetic beam, such as an electron beam, is directed at a selected IC location. The IC has a layer of a solid, fluid or gaseous reactive material, such as a directed stream of a fluorocarbon, formed over the surface of the IC. The energetic beam disassociates the reactive material in or on the region into chemical radicals that chemically attack the surface. The surface may be examined as various layers are selectively removed in the controlled area spot etch, and SEM imaging may then be used to diagnose problems.

TECHNICAL FIELD

This application relates generally to semiconductor devices and devicetesting and, more particularly, to analysis of manufacturing defects anderrors associated with electrical function failure and long termreliability failure in integrated circuit (IC) devices, which may beindividual die, packaged die or die still on semiconductor wafers, suchas memory devices, logic devices and microprocessors.

BACKGROUND

The semiconductor device industry has a market driven need to reduce ICdevice failures at electrical test, and to improve the operationallifetimes of IC devices. Reduced device failures may result in increasedIC fabrication yield and improved device operational lifetime. IncreasedIC fabrication yields may result in decreased IC prices, and improvedmarket share.

One method to reduce the number of device failures is to analyze faileddevices and determine the cause of the failure. The failures may be whatare known as field failures that occur at customer sites, or they mayoccur in products that have been sold to consumers. The failures may befound during wafer level testing at the end of wafer fabrication, or intesting after a supposedly good IC die is placed in a package, or intesting after a supposedly good IC package is placed in a printedcircuit board (PCB).

It is known to examine failed devices by means of electrical testing,optical microscopes, transmitting electron microscopes (TEM), scanningelectron microscopes (SEM), focused ion beams (FIB), and other wellknown methods. If, for example, a particle is found that produces ashort between two conductive lines in a signal layer, then action may betaken at the fabrication site to reduce particle levels, and thusincrease fabrication yield. This method may be used in cases where thefailure, such as the illustrative particle just discussed, is at, ornear, the surface of the sample, since the failure may not be otherwisevisible in an optical or an electron microscope.

If the cause of the device failure is not on the surface of the sample,it is known to cut or fracture the device at a location near thesuspected failure site, set the fracture surface in a holding mechanism,such as epoxy, and grind or polish the exposed lateral edge down toapproximately the failure location. The location beneath the devicesurface may then be seen in cross section by SEM or optical microscope,and the nature of the defect may be observed.

Another method to reduce the number of device failures is to examinetest structures fabricated along side the production semiconductorwafers to determine if each production step has been completed withinthe specified tolerances. These tests may be electrical or physical, andmay be destructive tests, such as physically measuring the amount ofpressure required to pull a metal layer off of the surface. It is alsoknown to make such destructive tests on small portions of productionwafers, such as by using the non-functional area between IC die, whichmay be known as scribe lines or streets, to form the test structures.However, such tests may not accurately reflect the actual situation onthe production IC die, since the scribe lines may not be treated exactlythe same as the IC die, for example in not having the same area densityof dielectric as a real circuit area.

Another method of testing to determine if each production operation hasresults that are within the specified range, is to deconstruct orreverse process a small area on a production IC die. For example, it isknown to remove the top layers of an IC device by means of what may beknown as a spot etch, in which a small elastomeric ring formed of achemically resistant material is pressed onto the surface of the IC inthe area of the suspected defect and serves to hold an etching solutiondesigned to selectively remove some or all of the top layers of thestructure and expose potential defects. For example, it is possible touse a chemical solution that preferentially attacks oxide layers toremove the passivation oxide over a polysilicon structure, and determineby SEM examination if a non-oxide dielectric layer under the polysiliconhas been properly etched. However, the size of the elastomeric ring isvery large as compared to the dimensions of typical IC structures, andmay be larger than 2 mm in diameter, and thus produces a relativelylarge hole in the IC device. Further, there is no method to image thesurface during the material removal process to determine if the lateralpositioning is correct, or to determine if the depth of the materialremoval has reached the desired location. Thus, the spot etch, ordeconstruction etching, must be done using timed etches and assumed orestimated etch rates. The use of liquid etch materials also limits thesize of the hole that may be etched, since very small holes may haveproblems with reactant exchange with the bulk of the etch media,reactant depletion, and surface wetting problems including bubbleformation. Such wetting, depletion, and other etch initiation problems,also contribute to the variability in etch depth.

It is known to etch small diameter holes of several microns in diameterin IC surfaces by means of what may be known as ion milling, usingfocused ion beams of such heavy ions as gallium. It is possible toanalyze the material being etched by examining the atoms in the exhaustgas, typically using optical emission, atomic absorption, infrared,Raman, or mass spectroscopy. However, ion milling is generally notselective etching of materials, such as oxide over metal or polysiliconas in the previously discussed example. Such selective etch rates may bereferred to as having an etch ratio. Ion milling may be compared to theuse of a drill, cutting everything in its path relatively equally versusthe high selectivity available with the chemical spot etching discussedabove.

A method is needed to chemically etch a small area with high selectivitybetween different material etch rates, and the ability to observe theetching. The ability to analyze the composition of the material beingetched would also be beneficial in determining the cause of a failure.With such an arrangement, the sample may be imaged during the small spotetching, and the etching may continue until the desired structure iscompletely exposed and ready for testing. Further, analysis of materialsthat may appear unexpectedly during the progress of etching may also beperformed.

BRIEF DESCRIPTION OF THE DRAWINGS

The abovementioned issues are addressed by the present disclosure andwill be understood by reading and studying the following specification,of which the Figures are a part.

FIG. 1 illustrates a semiconductor device seen in cross section;

FIG. 2 illustrates the semiconductor device of FIG. 1 in a vacuumchamber and locally etched in accordance with an illustrativeembodiment;

FIG. 3 illustrates the semiconductor device of FIG. 1, after a period ofetching has occurred in another illustrative embodiment;

FIG. 4 is a flowchart of the method in accordance with an illustrativeembodiment;

FIG. 5 is a block diagram of an electronic device in accordance with anembodiment of the invention; and

FIG. 6 is a diagram of an electronic system having devices in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific aspects and embodiments inwhich the present disclosure may be practiced. These embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the present disclosure. Other embodiments may be utilized andstructural, logical, and electrical changes may be made withoutdeparting from the scope of the present disclosure. The variousembodiments are not necessarily mutually exclusive, as some embodimentscan be combined with one or more other embodiments to form newembodiments.

The term “horizontal” as used in this application is defined as a planeparallel to the conventional plane or surface of a wafer or substrate,regardless of the orientation of the wafer or substrate. The term“vertical” refers to a direction perpendicular to the horizontal asdefined above. Prepositions, such as “on”, “side” (as in “sidewall”),“higher”, “lower”, “over” and “under” are defined with respect to theconventional plane or surface being on the top surface of the wafer orsubstrate, regardless of the orientation of the wafer or substrate. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present disclosure is defined onlyby the appended claims, along with the full scope of equivalents towhich such claims are entitled.

The disclosed embodiments provide a method for localized selectivechemical etching of an integrated circuit (IC) in preparation fortesting and problem diagnosis. In an embodiment, the localizedselectivity accelerator is an electron beam, and the excited material isa halogen containing compound forming a layer on, or immediately above,the surface of the IC in a vacuum chamber, such as inside a scanningelectron microscope (SEM). Localized electron beam assisted chemicaletching provides a method of localized materials characterization, suchas may be useful in IC failure analysis. This method allows forselective and/or sequential etching of various layers, and may becompared to what is known in the art as spot etching. It is alsopossible to use the described method to selectively deposit materialslocally, for example, in the etched hole. For example, a one microndiameter hole may be etched through several different material layers ofan IC chip, and an unopened contact may be probed, or perhaps etchedopen by the use of appropriate etch compounds. The hole may then befilled with a conductive material and a dielectric material using theelectron beam method to create radicals of silane and oxygen to form asilicon oxide dielectric layer in the hole. The “repaired” device maythen be removed from the system and electrically function tested todetermine if the contact was the sole cause of the observed failure.

IC structure characterization and diagnosis may occur, in anillustrative embodiment, by passing a gas phase halogen containingmaterial over the surface of the IC chip in the vacuum chamber, andexciting the halogen atoms with an electron beam to form chemicalradicals. By controlling the vacuum pressure and the gas flow, the meanfree diffusion length of the radicals may be controlled, and the etchingof the IC surface may be confined to a desired region around theelectron beam. Electrons from the primary beam, electrons scattered fromthe IC surface, as well as secondary electrons from the IC surface mayall cause the formation of the halogen radicals by dissociating theindividual atoms of the halogen containing layer. The halogen containinglayer may be adsorbed onto the surface of the IC, as may occur whenusing a base material such as xenon difluoride, which sublimates in avacuum and may deposit on the surface of the IC.

The radicals may selectively, or non-selectively, etch portions of theIC surface, depending upon the selected combination of chemicals, andthe etch products may be removed from the surface of the IC by thevacuum system pump. The removed materials may then be analyzed by avariety of down stream systems, such as a residual gas analyzer (RGA),to provide material characterization or to indicate that a specificlayer has been substantially completely etched. The characterization maybe done continuously until a desired depth is reached in the IC surface,or may be done at selected intervals, or when an interesting item isobserved in the SEM view. This method provides a combination of chemicaland spatial information as a function of depth while removing layers ofthe IC, which may be known as deprocessing.

FIG. 1 illustrates a semiconductor device 100, having a substrate 102,with a series of conductive regions 104. The conductive regions 104 maybe formed from diffused portions of the substrate 102, from dopedpolysilicon, or from various metals and metal silicides. The conductors104 are covered with a dielectric layer 106, having conductor filledcontacts 108. The contacts 108 connect the conductive regions 104 toconductive regions 110, to form device signal and powerinterconnections, a contact test chain, or other structure. The variousconductive materials may be pure materials or combinations of materials,such as copper doped aluminum, or may be formed of multiple layers, suchas titanium tungsten barrier layers under each of the conductors 110.The conductors 110 are protected from environmental problems such asscratches and ionic contamination by a dielectric layer 111, which maybe planarized to improve the topography for layers above the dielectriclayer. One known method of planarizing a dielectric layer is chemicalmechanical polishing (CMP). The dielectric layer 111 may have adifferent thermal coefficient of expansion (TCE or CTE) compared to thesubstrate 102, and thermal stress cracks 112 may occur. Cracks 112 maybe a reliability issue since contaminants may travel into thesemiconductor device via the crack. The use of CMP planarization maycause surface scratches 114, which may be difficult to distinguish fromcracks 112, but may not be a serious reliability or yield problem. Themethod described herein may allow diagnosis of the potential problem aseither a crack 112, a simple CMP scratch 114, by allowing the dielectric111 to be observed as the region around the crack 112 or scratches 114is locally etched. In an embodiment, the hole in the dielectric 111etched by the described method may then be refilled by local dielectricdeposition, for example using oxygen gas and silane gas exposed to theenergetic beam, such as an electron beam.

The dielectric layer 111 is covered in the illustrated embodiment withanother dielectric layer 116, having a structure 118 and 120 embeddedtherein. Examples of such structures may be a multilayered capacitor 120connected to the rest of a circuit fabricated on substrate 102 by anelectrically conductive material 118, which may be a titanium tungstenlayer, or a doped polysilicon layer among many possible conductivematerial choices. The reliability of the illustrative capacitor 120 maydepend upon how well it adheres to the layer 118, which may be affectedby many factors, including whether the layer 118 has been excessivelyundercut during processing, as shown in the figure. The present methodprovides a method of removing the dielectric layer 116, so that testingof the capacitor 120 may be performed. Examples of tests that may bedesired include shear strength tests and vibration resistance testswhich check to see if any of the structures 120 topple.

FIG. 2 illustrates the semiconductor device of FIG. 1 in a vacuumchamber 232, in an embodiment, a SEM, having a vacuum pump (not shownfor simplicity), an inlet 234, and an energetic beam 236, such as anelectron beam, which may be movable. The inlet 234 may be a directed gasjet as shown, or a sublimation port, a gas shower head, or a liquidmaterial sprayer, such as an atomizer. The inlet 234 supplies the regionaround the top surface of the sample with a material that is eitherreactive, or may be made reactive, such as a halogen containingmaterial. The atoms of the halogen in this illustrative example areshown as floating “H” symbols, some of which are adsorbed onto thesurface of the sample, and some diffusing around the chamber 232.

The vacuum chamber 232 has a directed and focused energetic beam device236, which in an embodiment is a SEM beam, directed to a desiredlocation on the surface of the sample. The electron beam device 236emits electrons 238 (shown as “e⁻” symbols) which excite the halogenmolecules or atoms (H) floating in the vacuum chamber 232, or adsorbedonto the surface of the sample, and form a chemically reactive radical,denoted by “H*”. Due to short radical lifetime, the radicals are limitedto the area around the electron beam 236 shown by the dotted lines. Theselected radicals H* have a much greater chemical etch rate on thedielectric layer 216, than the halogen molecules or atoms (H), and thusthe etching of the two shown pits occurs wherever the illustrativeelectron beam forms the H radicals. In an illustrative embodiment, thehalogen compound is xenon difluoride, which forms fluorine radicals whenexcited by the electron beam. The fluorine radicals have a large etchrate on the top dielectric layer 216, but does not rapidly etchconductive materials such as 220 and 218. In this example, the etchingis said to be selective for dielectrics over conductive materials. Insuch a fashion, it is possible to etch pits in the dielectric 216 toexamine the crack 212 and scratches 214, or to remove the dielectric 216from around the illustrative capacitor 220, which is shown as havingpoor adherence to the contact 218, and thus toppled during a vibrationor turbulence test.

FIG. 3 illustrates another illustrative embodiment of the device of FIG.1, after a period of etching of the dielectric layers 316 and 311 abovethe conductive lines 310 has passed. In this illustrative embodiment,the capacitor shown in FIG. 1 is at a different location than the etchedlocation shown. The material being removed may be analyzed by any of thedown stream methods previously discussed, such as RGA, in order todetermine when the etch surface has reached the conductive material 310.In addition, the etch stop upon reaching the conductive material 310 maybe determined directly using the SEM.

In this illustrative embodiment, the potential problem to be diagnosedis the electrical continuity of the illustrated contact chain made ofconductive materials 304, 308 and 310. Once the hole has been etched tocontact the conductive material 310, it may be probed by making physicalcontact with a test probe, but it may be seen that the etched hole mayonly be one micron in diameter, and no physical probe can reliably reachinto such a small opening. In an embodiment, the exposed conductor 310is electrically charged by the shown electron beam 236, and thecontinuity is observed by use of the voltage contrast mode of the SEM.In such a fashion, it is possible to determine if a contact chain has adefect such as an open circuit caused by an inadequately etched contact,or if there is a large voltage drop at a specific location in thecontact chain. It may also be possible for the device to be repaired bybuilding up a sufficient voltage to rupture the unopened contact. Such aprocedure may have reliability risks, such as time dependent dielectricbreakdown of transistor gate dielectrics that may be connected in somefashion to the contact chain.

In an embodiment, the etch pit is locally refilled by changing thematerial injected into the vacuum chamber 332 by the injector 334 toinclude a dielectric deposition gas mixture, such as silane and oxygen,which may react rapidly in the presence of the electron beam from device336, and preferentially grow a dielectric layer in the hole over theconductor 310. The repaired device may be removed from the vacuumchamber 332, and electrically function tested in any common method, todetermine if the device may be operated normally.

FIG. 4 is a flow diagram showing the method for electron inducedchemical etching for device level diagnosis of potential problems. Themethod starts at 402 with obtaining a sample, such as an IC, fordeconstruction. At 404 the sample is placed in a vacuum chamber, such asa SEM, and the chamber begins to be evacuated at 406. At 408 it isdecided whether or not the chamber has been pumped to a desired vacuumpressure, which may be used to control the mean free path of theradicals generated by the electron beam. If the desired pressure is notyet obtained, the method returns to 406. When the proper vacuum level isreached the method uses a beam locator device, such as a SEM, to findthe desired location at 410. At 412, the reactive material is injectedinto the vacuum chamber at a controlled rate, which in conjunction withthe control of the vacuum pressure and the beam energy and intensity,may determine the production rate of the chemical radicals. The electronbeam is turned on at a desired energy and beam intensity at 414, whichdepending upon the selected reactive material composition and pressurebegins the chemical etching of at least some portion of the samplesurface towards which the electron beam is directed. The reactionproducts are removed by the vacuum system.

At 416, the surface is examined by imaging the etch region with a SEM,and determining if the desired IC layer location has been reached. Anendpoint to the etching may be directly observable by a SEM, or thereaction products may be analyzed by any of a variety of down streamanalytic methods, such as RGA, to determine if the material being etchedhas been substantially removed. The exposed surface may also be analyzedby SEM based analysis methods, such as EDAX or XES to determine if thedesired location, such as the conductive layer 310 of FIG. 3. At 418 itis determined whether the current material has been etched sufficiently.If not the method returns to 412 until the current layer has been etchedto a desired depth.

If the current layer etching and analysis has been completed, then it isdetermined at 420 if there is an additional layer that needs to beetched, or whether there is to be a localized deposition done to fillthe etched hole. If not, the method ends at 430, and the diagnostictesting may begin.

If there is another process to complete prior to ending the method, thena new reactive material may be injected into the vacuum chamber at 422,the electron beam is turned on to the desired energy level and intensityat 424, the etching maybe observed and the surface analyzed, and theetch result is analyzed at 426 as previously done at 416. At 428, it isdetermined if the present layer has been fully etched or deposited. Ifnot, the method returns to 422. If the layer etch is completed, themethod ends at 430.

FIG. 5 is a block diagram of a general electronic device in accordancewith an embodiment of the invention with an electronic system 500 havingone or more devices failure analyzed and tested and/or repairedaccording to various embodiments of the present invention. Electronicsystem 500 includes a controller 502, a bus 504, and an electronicdevice 506, where bus 504 provides electrical conductivity betweencontroller 502 and electronic device 506. In various embodiments,controller 502 and/or electronic device 506 include an embodiment for aportion of the device having an IC die characterized and/or repaired aspreviously discussed herein. Electronic system 500 may include, but isnot limited to, information handling devices, wireless systems,telecommunication systems, fiber optic systems, electro-optic systems,and computers.

FIG. 6 depicts a diagram of an embodiment of a system 600 having acontroller 602 and a memory 606. Controller 602 and/or memory 606include a portion of the circuit having IC devices and memory chipscharacterized and/or repaired in accordance with the disclosedembodiments. System 600 also includes an electronic apparatus 608, and abus 604, where bus 604 may provide electrical conductivity and datatransmission between controller 602 and electronic apparatus 608, andbetween controller 602 and memory 606. Bus 604 may include an address, adata bus, and a control bus, each independently configured. Bus 604 alsouses common conductive lines for providing address, data, and/orcontrol, the use of which may be regulated by controller 602. In anembodiment, electronic apparatus 608 includes additional memory devicesconfigured similarly to memory 606. An embodiment includes an additionalperipheral device or devices 610 coupled to bus 604. In an embodiment,controller 602 is a processor. Any of controller 602, memory 606, bus604, electronic apparatus 608, and peripheral device or devices 610 mayinclude ICs treated in accordance with the disclosed embodiments. System600 may include, but is not limited to, information handling devices,telecommunication systems, and computers. Peripheral devices 610 mayinclude displays, additional memory, or other control devices operatingwith controller 602 and/or memory 606.

CONCLUSION

A method is presented for IC problem diagnosis by positioning the samplestructure in a vacuum chamber, and creating a layer of a reactivematerial either on or in proximity with the surface of the IC. The layerof reactive material is excited to form chemical radicals, which removea portion of the surface of the structure by chemical etching until thedesired layer is reached, or the structure is exposed. The materialremoved from the surface may also be analyzed to characterize thematerial in various ways. With such an arrangement, the variousstructures in an IC chip may be exposed, undercut and prepared fortesting of the layer properties. The method may also be used to formlocalized depositions of dielectric or conductive materials.

The reactive material may comprise various types of halogen in gaseous,liquid or solid form. In an embodiment, the reactive material is xenonfluoride, which is a solid at standard temperature and pressure, andsublimes in the vacuum chamber. The reactive material may be directed tothe region near the surface of the IC chip by a formed jet of vapor ormay simply be allowed to diffuse through the vacuum chamber. Thereactive material may be adsorbed onto the surface of the material, maybe a gas in the vicinity of the surface, or may condense or precipitateonto the surface. The reactive material may be a mixture of materials(that is chemical precursors) which react with one another, especiallywhen activated or excited to form chemical radicals, and may include amaterial that does not directly interact with the other reactivematerials, but rather acts as a reaction catalyst, an inhibitor,promoter, or reaction buffer. The chemical radicals may form a chemicaletching environment that may selectively remove one component of thematerial to be characterized, and the precursor reactive materials maybe changed as the process continues and as different materials areuncovered on the IC.

The method of exciting the layer of reactive materials may use anenergetic beam such as an electron beam. The electron beam may have adiameter of about 0.1μ, or may be less than 0.01μ, or greater than 1.0μ,depending upon the size of the area that is to be deconstructed.Preferably, the electron beam diameter is 0.005μ, and the area ofexcited reactive materials is formed by scanning the beam over thedesired area. The electron beam may have a lower energy or beamintensity to slow the etch rate to improve etch control, or may bedefocused to etch a wider area. The electron beam may be scanned tocover the desired etch area or etch shape. The etch areas may be made assmall as the electron beam can focus, plus the mean free path of thegenerated chemical radicals, and may have a diameter of less than 1.0μ.The electron beam may be part of a scanning electron microscope (SEM),and the SEM may be used to provide an image of the process as etchingoccurs.

The surface material removed by the chemical radicals may be analyzed bywell known analytical methods, including downstream analysis systemssuch as residual gas analyzer (RGA), mass spectroscopy, optical emissionspectroscopy, atomic absorption spectroscopy, infrared spectroscopy,Raman spectroscopy. The surface may be direct spot analyzed by variousmethods such as energy dispersive analysis of X-rays (EDAX), XES, orother SEM based analytic methods. This analysis may continue while theetch process is occurring to provide a material characterization versusdepth analysis. Such analysis of removed material may assist indetermining when the desired layer has been substantially removed, andmay thus serve as an etch stop indicator, as well as indicating when anunexpected material is present.

The material to be etched may be selected by choosing a chemical radicalthat preferentially etches one material faster than other materials,such as fluorine radicals etch silicon oxides and glasses at a muchhigher rate than they etch metals or organic materials. By using aradical chemistry that has a high etch ratio for oxides, it is possibleto substantially completely remove a glass layer surrounding a trenchcapacitor without harming the metal plates of the capacitor or thedielectric layer. In such a manner, a device such as a trench capacitormay be examined on an IC, and various tests may be preformed on thecapacitor, such as undercutting and adhesion tests.

In an embodiment, the vacuum chamber and electron beam are a part of ascanning electron microscope (SEM), and the etching may be observed bymeans of the SEM. In such an arrangement, the dielectric over a seriesof metal to metal contacts may be etched away, thus exposing at leastone portion of the metal. The electron beam of the SEM may then be usedto charge the entire string of metal to metal connections, and the SEMvoltage contrast mode may be used to observe which of the contact stringhave badly opened or highly resistive contacts.

In an embodiment, the etching of a dielectric layer may be observed asthe etching continues, or during short duration breaks between etchcycles, to determine if artifacts in the dielectric layer are surfacescratches, such as those commonly seen after a dielectric layer has beenplanarized by means of chemical mechanical polishing (CMP), or whetherthe surface artifacts are cracks in the dielectric layer, such as may becaused by thermal stress in various types of brittle protective glasslayers, such as boron-phosphorus silicate glass (BPSG).

Another illustrative embodiment of the invention includes a system forlocalized accelerated chemical etching, including a vacuum chamber and afixture for positioning a sample, a system, such as a gas inlet jet, forcreating a layer of a chemical proximate to the surface of the sample.An energetic beam, such as an electron beam from a SEM, is directed atthe surface of the sample to form chemical radicals in the chemical,such as xenon difluoride, which may etch the sample in the region aroundthe site of the energetic beam. The removed material may be analyzed todetermine both the composition of the surface of the sample, and asetching continues to a desired depth. The depth may be observed duringthe etch process by the SEM or other imaging device, and the compositionof contaminants may be determined by the analysis device. Areas smallerthan one micron in diameter may be etched to expose various processlayers, which may then be examined for proper processing, such asappropriate slope of reflowed dielectric layers, or beveled edges oncontact openings.

The described embodiments are directed towards the use of an electronbeam to activate an adsorbed material forming a layer on an IC chip, andforming chemical radicals to etch the surface material of the IC, butthe embodiments of the invention are not so limited, and may be appliedto other structures and devices, such as printed circuit boards (PCBs),multi-chip modules MCMs), liquid crystal display (LCD) devices,electronic displays, micro-electromechanical devices (MEMs), or othermanufactured electronic or mechanical devices requiring failure analysistesting and material identification. Other means of forming localchemical radicals other than electron beams are included in thisdisclosure, to include focused microwave beams, laser and maser beams,X-ray and other energetic radiation sources. The material used to formthe chemical radicals may be a gas, an evaporated liquid, a sublimedsolid, or may be chemically formed by mixing precursor materials at thesurface of the structure to be analyzed, or mixed remotely from thesurface and either passively or actively transported to the regionaround the surface of the IC, or other structure. The reactive materialmay be either adsorbed onto the surface, precipitated onto the surface,or form a fluid layer in proximity to the surface, including a gaseouslayer in the region around the IC surface. The generated chemicalradicals may be used to selectively etch the surface as described in thedescribed embodiments, or may react with other provided, or alreadypresent materials, to form dielectric, conductive or other materials tobecome a local deposition reaction. Such depositions may be used torefill the previously etched region to return the IC to workingcondition.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for the specific embodiments disclosed, described andshown. This application is intended to cover any adaptations orvariations of embodiments of the present invention. It is to beunderstood that the above description is intended to be illustrative,and not restrictive, and that the phraseology or terminology employedherein is for the purpose of description and not of limitation.Combinations of the above embodiments and other embodiments will beapparent to those of skill in the art upon studying the abovedescription. The scope of the present disclosure includes any otherapplications in which embodiments of the above structures andfabrication methods are used. The scope of the embodiments of thepresent invention should be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

1. A method of diagnosing a problem in a structure, comprising:positioning an integrated circuit having a structure to be evaluated ina vacuum chamber; creating a layer of a reactive material a selecteddistance above and in proximity with a surface of the integratedcircuit; exciting a portion of the layer of reactive material a selecteddistance above and in proximity to the structure to be evaluated to formchemical radicals above and in proximity to the surface of the structureto be evaluated; removing a portion of the surface of the integratedcircuit in proximity to the structure to be evaluated to a selectedlevel to evaluate an exposed electrical structure of the integratedcircuit; and continuing the creating, exciting and removing steps untila stop criterion occurs, wherein the exposed electrical structure isevaluated to determine the presence or absence of a potential problem byat least one of a shear strength test, a vibration test, a turbulencetest, a tilt test, an adhesion test, a thermal cycle test, anenvironmental test, and an electrical test.
 2. The method of claim 1,wherein the removing a portion of the surface includes etching at leastone dielectric layer surrounding an electrical structure on theintegrated circuit to expose at least a top side and a plurality oflateral sides.
 3. The method of claim 1, wherein the removing a portionof the surface includes etching at least one dielectric layer andevaluating the depth of cracks in at least one dielectric layer.
 4. Themethod of claim 3, wherein the etching of the at least one dielectriclayer ends when the depth of the cracks is less than the thickness ofthe at least one dielectric layer, and removed portion of the at leastone dielectric layer is locally filled by a local deposition of adielectric material formed by exciting a second reactive material inproximity with the surface of the integrated circuit.
 5. The method ofclaim 1, wherein the removing a portion of the surface includes etchingat least one dielectric layer and stopping the etching at a surface of aconductive material layer.
 6. The method of claim 5, wherein thereactive material is removed from the proximity of the surface of theintegrated circuit, and an electron beam having a predetermined energy,dwell time and current density is incident upon the conductive materiallayer exposed by the etching.
 7. The method of claim 6, wherein theconductive material exposed by the etching is a portion of a pluralityof conductive objects electrically interconnected by contact holes andis electrically charged to a predetermined level by the incidentelectron beam.
 8. The method of claim 7, wherein electrical conductivityof the conductive material and the contact holes is determined.
 9. Themethod of claim 8, wherein a scanning electron microscope is used todetermine the electrical conductivity of each one of the plurality ofconductive objects and contact holes.
 10. The method of claim 1, whereina stop criterion includes a scanning electron microscope imageindicating that the structure to be evaluated is exposed.
 11. The methodof claim 10, wherein the reactive material comprises a halogen.
 12. Themethod of claim 11, wherein the reactive material is xenon fluoride. 13.The method of claim 10, wherein the reactive material is a gas.
 14. Themethod of claim 10, wherein the reactive material is a mixture ofmaterials capable of reacting with one another.
 15. The method of claim14, wherein the mixture of reactive materials includes at least onematerial that does not directly interact with the other reactivematerials.
 16. The method of claim 10, wherein exciting the layer ofreactive materials comprises an electron beam.
 17. The method of claim16, wherein an area containing the chemical radicals has a diameter ofless than 1.0μ.
 18. The method of claim 17, wherein the radicalscomprise a chemical etching environment disposed to remove at least onecomponent of the material to be characterized.
 19. The method of claim18, wherein the reactive material is changed as the chemical etchingoccurs to selectively remove different components of the material to becharacterized.
 20. The method of claim 1, wherein a stop criterionincludes analyzing the material removed from the surface and ending thecreating a layer of reactive material in proximity to the surface when achange occurs in a composition of the material removed from the surface.21. The method of claim 20, wherein analyzing the material removed fromthe surface includes at least one of residual gas analysis, massspectroscopy, optical emission spectroscopy, atomic absorptionspectroscopy, infrared spectroscopy and Raman spectroscopy.
 22. Themethod of claim 21, wherein the material analysis continues as thechemical radicals etch into the surface of the material to produce amaterial characterization versus depth analysis.
 23. The method of claim1, wherein the exciting the layer of reactive material to form chemicalradicals includes an electron beam incident on the surface of theintegrated circuit.
 24. The method of claim 23, wherein the electronbeam comprises a portion of a scanning electron microscope disposed toprovide an image of the integrated circuit surface during the removing aportion of the surface.
 25. The method of claim 1, wherein a vacuumpressure of the vacuum chamber is determined by a desired mean free pathof the chemical radicals generated by the exciting the layer of reactivematerial in proximity to the surface.
 26. The method of claim 1, whereinthe reactive material is changed as the chemical etching occurs toselectively remove different components of the integrated circuit. 27.The method of claim 26, wherein the reactive material is changed from anetching radical to a combination of reactive materials forming adeposition radical mixture.
 28. The method of claim 27, wherein thedeposition radical mixture comprises at least one of silane,dichlorosilane, trichlorosilane, silicon tetrachloride, oxygen, watervapor, hydrogen peroxide and nitrous oxide.
 29. The method of claim 27,wherein the etched region is at least partially filled by a dielectriclayer.